1. Field of the Invention
The invention relates to a device for electrostimulation therapy with at least one circuit with a pair of electrodes, at least one amplifier, an impulse oscillator, a program memory and an input unit as well as a control unit.
2. Description of the Prior Art
Devices of this type for electrostimulation therapy, and particularly for electrical interference therapy, in other words, a therapy by which medium frequency voltages with frequencies in the range of a few thousand Hz are applied over at least two circuits each with one pair of electrodes, which differ from each other by a low frequency range of from a few to a few hundred Hz, so that stimulations, and thereby therapeutically effective oscillations called beats, occur with correspondingly low frequency in the body, are known. Devices of this type work basically satisfactorily and have a remarkable effectiveness and success of treatment.
Problems of the medium frequency voltages with known analogous devices, in that the frequency difference giving the beat frequency - caused by interference of the medium frequencies - signals particularly if quite small, cannot be held sufficiently stable, since it is influenced by outside factors, such as temperature, feed voltage, humidity, aging of material and scatter values of the modular components.
With the development of electronic digital technology, the problem of stability has been solved in large measure by digitization. Sufficient stability of the beat frequency can be attained digitally. In digital technology, however, low beat frequencies can be produced only with very extensive technical and financial outlay. A high-frequency, quartz-controlled oscillator is used for this purpose, of which the frequency is divided down in two different ways, i.e., by two different divider ratios by means of digital elements. The smaller the desired frequency difference of the medium frequency oscillations, the higher the oscillator frequency and the larger and more expensive the outlay will be for dividing down the frequency and for producing small frequency differences of the medium frequency output oscillations.
This problem arises particularly when a dense frequency spectrum must be made available for the treatment, i.e., on the one hand, when various closely-spaced beat frequencies must be supplied, and, on the other hand, when the treatment requires that this frequency spectrum be run through quasicontinuously or possibly periodically, i.e., for example, between 5 and 20 Hz in a time period of 10 to 15 seconds. The high resolution required for this, i.e., the spacing between two adjacent beat frequencies, (e.g. 10 Hz and 10.1 Hz) to be run through in succession, can be attained in digital technology only at very high cost. For example, with two current circuits with medium frequency each in the range of ca. 4 thousand Hz and a desired resolution--i.e., the lowest frequency spacing between the two medium frequencies or the smallest "step" for changing the beat frequency--of one must operate with a pulse frequency of 160 MHz. The use of a pulse oscillator and frequency divider with such a high frequency is neither technically nor commercially justifiable in mass production of electrical interference devices.
Another problem is that, in the devices described above, with reasonable technical outlay, it is not possible to attain of various curve shapes, both the medium frequency output signals and the beats.
In order to solve the last problem with known devices of this type, the procedure is to store the various curves of medium frequency output signals in the usual known memory devices and to call them as needed. Such storage can be effected by analog means or, with the development of digital technology, and especially digital memories, by digital processes; the respective cited specific problems and drawbacks remaining the same in either case. This storage can be accomplished, for example, by means of disks, tape memories, core memories, using magnetic record technology or the usual solid state memory devices, such as large-scale integration (LSI) semiconductor memories, including ROM's i.e., Read Only Memories, PROE's, i.e., Programmable Read Only Memories, or even EPROE's, i.e., Erasable and Programmable Read Only Memories in an appropriate known manner. Reading can be accomplished by equally familiar addressing techniques, for example, directly from the keyboard to use a method a long known in the art. This approach is disadvantageous, in addition particularly to the already cited analog- or digital-specific problem, in that a very high memory outlay is needed for the required processing. Also, with inexpensive memories, such as tapes, the danger exists that the signal cannot be retrieved over a long time (years) with the same good and therapeutically necessary quality. Also, undesirable frequency fluatuation arise because of defective synchronization of tapes.